Ocean-Atmosphere Interaction in the Eastern Pacific ......TOGA-COARE Bulk Formula Plus, Winds...
Transcript of Ocean-Atmosphere Interaction in the Eastern Pacific ......TOGA-COARE Bulk Formula Plus, Winds...
Ocean-Atmosphere Interaction in the Eastern Pacific;Coupled Modeling Study
Hyodae Seo, Arthur J. Miller, John O. RoadsScripps Institution of Oceanography
A high-resolution ocean model (ROMS) has been coupled to regionalatmospheric model (RSM) to understand small-scale air-sea interactionprocess. Using the coupled modeling system, various aspects of ocean-atmosphere coupling in the eastern Pacific and the tropical Atlantic ocean areunder investigation. This poster illustrates a few examples on air-seainteractions near the tropics and in the midlatitude ocean of the easternPacific.
IC and Lateral BC:NCEP/DOE Reanalysis
Lateral BC: OceanAnalysis (JPL)
SST
TOGA-COAREBulk Formula
Plus, Windsrelative to ocean
currents
RegionalSpectral Model
(RSM)
Regional OceanModeling
System (ROMS)
Boundary LayerVariables
OceanAtmosphere
Snapshot of SST and wind-stress on Nov. 11, 1999 in the eastern TropicalPacific ocean domain by coupled model. Figure illustrates clear signal ofequatorial cold tongue and TIWs near the equator, and gap-wind induced coldtongue near Gulf of Tehuantepec, hint of Costa Rica Dome near the Gulf ofPapagayo.
Air-Sea Interaction in the Eastern Pacific
Coupled Modeling System
Introduction
Gap Winds and Air-SeaInteraction (25km ROMSand 28km RSM)
Air-Sea Interactionover TIWs (20kmROMS + 30km RSM)
1.
Air-Sea Interaction by Gap Winds in Central America
5-year model climatology clearly indicates that gap winds throughTehuantepec, Papagayo, and Panama exert Ekman forcing as well as wind-induced mixing and cooling on eastern Pacific warm pool. Cool region withinwarm pool in turn suppresses atmospheric deep convections and thusprecipitation of comparable size but 2 seasons later within ITCZ, as is observedby satellite (Xie et al., 2005).
2.
2.1 Atmospheric response to TIWsSST WS (N/m2)
WSC(N/m2 per 10^4 km)
LH(W/m^2)
SST, wind-stress (WS), WS curl (WS Curl), and latent heat (LH) flux fromJune to October in 1999 by coupled model. TIW-induced SST leads tomodification in wind-stress and its derivatives (Chelton et al. 2001 ) as well asturbulent flux fields (Thum et al., 2002); WS is in phase, WSC in 90 degreeout of phase, LH is 180 degree in phase with SST.
Effect of Atmospheric Feedback on characteristics of TIWs.
DYNM: 1-year run ofROMS with RSM wind-stress and climatologicalheat flux;
THERM:1-year run ofROMS with RSM heatflux and climatologicalwind-stress;
CPL: 1-year run ofROMS with RSMwixxnd-stress and heatflux;
The 1st EOFs (2nd EOFs are in 90 out of phase with similar varianceexplained) show that turbulent flux provides damping on TIW-induced SSTs(Chelton et al., 2004, Xie et al., 2004), while wind-stress leads to amplificationof TIWs; CPL shows intermediate intensity. Different atmospheric feedbackalso influences on the period, phase-speed, and initiation time of TIWs; heatflux produces TIWs earlier with shorter period (less than 30days) but more(~7) mostly east of 115W, while wind-stress produces 5 strong TIWs. Again,full coupling has intermediate characteristics of TIWs (cf. Pezzi et al., 2004).
Air-Sea coupling in southern California coastal ocean.SST (°C) WS Curl (N/m2 per 10^4 km)
WS Div N/m2 per 10^4 km) LH (W/m^2)
Effect of SST gradient on surface winds and turbulent flux fields are alsoevident over California coastal ocean on various spatial and temporal scales.Over short-lived cold filament off Pt. Reys, wind-stress curl (divergence) followisotherms where wind-stress are parallel (perpendicular) to them (Chelton et al.2001). The same patterns are observed over meander of current and associatedmeso-scale oceanic eddies (more evident in longer time mean, not shown).
ColdFilament
Meanderand eddy
Conv. (Div.) upwind(downwind) of coldfilament
Conv. (Div.) upwind(downwind) of meso-scale eddy
Positive/Negative WS-curlalong theisotherms
Negativefeedbackbyturbulentheat flux
2.2
1.
CPL EOF 1 Var=13.3% DYNM EOF 1 Var=12.5%
THERM EOF 1 Var=11.3% PC 1
3.Winter
Ekman Pumping Velocity(N/m^2 per 10^4km) SST (°C)
Precipitation(mm/day)
Coldtongue;Shoaling ofthermocline
Dry RegionswithinITCZ
EkmanUpwelling
EkmanDownwelling
Summer
TehuantepecPapagayo
Panama